The present application relates to suspension systems for vehicles. More specifically, the present application relates to a load dependent damper for a suspension system.
Dampers (e.g., dashpots, hydraulic shock absorbers, etc.) dissipate kinetic energy as part of a vehicle suspension system. Dampers often include a housing, end caps, a piston, and a rod that is coupled to the piston. Energy is dissipated through a hydraulic fluid flow along a hydraulic circuit (e.g., between a first chamber within the housing and a second chamber within the housing). The piston includes a plurality of orifices that are covered with a shim stack (e.g., a plurality of compressed shims). As the piston translates through the housing, hydraulic fluid is forced from the first chamber, through the piston, and into the second chamber. Specifically, pressurized hydraulic fluid is forced through the orifices within the piston, deflects a portion of the shim stack to create an opening, and flows into the second chamber by passing through the opening.
Such traditional dampers provide a damping force that does not vary based on the weight of the vehicle. The characteristics of the suspension system (e.g., the spring rate and damping rate) are tuned for a specific configuration. For example, a vehicle that is configured to carry a heavy load may have a relatively stiff suspension system that is capable of supporting the additional weight of the load. However, if the load is removed from the vehicle, the ride may be excessively stiff or over damped, thereby reducing ride quality for occupants of the vehicle. Conversely, if the suspension system is tuned for the unloaded condition, the vehicle may have a relatively soft suspension system not suited to support the additional weight in the loaded condition. By way of example, such a vehicle may have a suspension that is under damped in the loaded condition thereby reducing ride quality for occupants within the vehicle.
The suspension system may include a flow device coupled to an electronically controlled actuator to compensate for fluctuations in load weight. For example, an electronic actuator may be used to open or close one or more passages through a piston in the damper to adjust size or number of ports through which hydraulic fluid flows (e.g., bypass ports, etc.) thereby changing performance. However, such an electronic system adds additional cost and complexity to the vehicle suspension system. Further, the electronic components of the system (e.g., sensors, control modules, the actuator, etc.) may lack the appropriate level of durability to operate in adverse conditions.